1. Field of the Invention
The present invention relates to a signal processing method and, more particularly, to a signal processing method whereby an analog signal is converted into a digital signal, the converted signal is processed and the processed signal is restored into an analog signal. Advantageously, the analog-to-digital conversion can be performed by converting the analog signal to an intermediate signal, in an exemplary case, a pulse-width-modulated (PWM) signal, and digitizing the PWM signal. An apparatus particularly adapted to carry out the signal processing method is also disclosed.
Korean Patent Application No. 93-14196 is incorporated herein by reference for all purposes.
2. Description of Related Art
In digital audio/video systems, since digitized signals are more resistant to noise during recording or transmitting, an analog audio/video signal is converted into a digital signal and then processed, e.g., recorded as digital information onto a recording medium or transmitted via a transmission path. Thereafter, the recorded digital information is read out from the recording medium and reproduced as an analog signal, or the received digital signal is restored to the original analog signal, respectively.
Such systems include both an analog-to-digital (A/D) converter for converting an analog signal into a digital signal and a digital-to-analog (D/A) converter for converting the digital signal into an analog signal. It will be noted that, when the analog signal is digitized, it is sampled at a predetermined rate and, customarily, each sampling signal is converted into a digital signal represented by four, eight, sixteen or thirty-two bits.
According to the conventional method of processing an analog audio or video signal, since the A/D converter, which handles a large number of bits for high-resolution output, is used, the configuration of the A/D converter is complex. Moreover, since the amount of digitized information is cumbersome, the memory size required in implementing digital processing becomes overly large.
U.S. Pat. No. 4,509,037 discloses a delta modulation encoder including means for generating an analog dither signal from an analog image signal, a spectrum tilter for generating a flattened signal from the analog dither signal, a single-bit analog-to-digital converter for generating a digital output from the flattened signal, and means for sampling and providing a digital output and then converting the sampled output into an internal analog signal to be fed back to the dither signal generator. It will be noted that this apparatus tilts the analog dither signal, performs one-bit digitization in response to the phase of the tilted analog dither signal, and samples the digital signal.